JP2010087748A - Information processing apparatus and method, display, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the circuit scale of an OFDM receiver. <P>SOLUTION: In Fig.4, A of Fig.4 below an OFDM symbol indicates a first-time DFT calculation range which serves as a reference calculation range and B of Fig.4 indicates a second-time DFT calculation range without phase correction. The second-time DFT calculation range indicated by the B of Fig.4 deviates by an amount of l from the first-time DFT calculation range indicated by the A of Fig.4. So, as indicated by C of Fig.4, data Dl corresponding to the deviation l out of the OFDM symbol falling within the second-time DFT calculation range is moved to the tail end of the second-time DFT calculation range and then DFT calculation is performed. In other words, a range of data indicated by D of Fig.4 is a second-time DFT calculation range with phase correction. This invention can be applied to an OFDM receiver, for example. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an information processing device and method, a display device, and a program, and more particularly to an information processing device and method, a display device, and a program that can reduce the circuit scale of an OFDM receiver.

  As a modulation of the terrestrial digital broadcasting system, a modulation system called an orthogonal frequency division multiplexing (OFDM) system is used (see, for example, Patent Document 1).

  The OFDM scheme refers to the following scheme. That is, a large number of orthogonal subcarriers (subcarriers) are provided in the transmission band. Data is assigned to the amplitude and phase of each subcarrier. Then, digital modulation is performed by PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation). Such a system is the OFDM system.

  In the OFDM scheme, the transmission band is divided by a large number of subcarriers. For this reason, the band per subcarrier wave is narrowed and the modulation speed is slow, but the total transmission speed is the same as the conventional modulation system.

  In the OFDM scheme, data is allocated to a plurality of subcarriers. For this reason, it has the characteristic that a transmission / reception circuit can be comprised by using the following arithmetic circuits. That is, an IFFT (Inverse Fast Fourier Transform) arithmetic circuit that performs inverse Fourier transform at the time of modulation can be used. At the time of demodulation, an FFT (Fast Fourier Transform) arithmetic circuit that performs Fourier transform can be used. The FFT is one of algorithms for calculating a discrete Fourier (discrete Fourier transform, hereinafter abbreviated as DFT) very efficiently.

  In addition, the OFDM scheme has a feature that multipath tolerance can be improved by providing a signal section called a guard interval, which will be described later. Furthermore, it has the characteristic that it can utilize for the estimation of a synchronization or a transmission-line characteristic by inserting the pilot signal mentioned later discretely in a time direction or a frequency direction.

Because of these characteristics, the OFDM system is often applied to terrestrial digital broadcasting that is strongly affected by multipath interference. As digital terrestrial broadcasting adopting the OFDM system, for example, there is a standard such as DVB-T (Digital Video Broadcasting-Terrestrial). In addition, there is a standard such as ISDB-T (Integrated Services Digital Broadcasting-Terrestrial).
Japanese Patent Laying-Open No. 2005-303440

  However, if the start position of the DFT operation for the OFDM signal is shifted, the phase of the signal after DFT will rotate. For this reason, conventionally, a rotator for correcting this rotation is provided after the FFT operation circuit, which contributes to an increase in circuit scale.

  The present invention has been made in view of such a situation, and is intended to reduce the circuit scale of an OFDM receiver.

  An information processing apparatus according to an aspect of the present invention is generated by copying an effective symbol generated by dividing information into frequency components within a predetermined band and a signal waveform of a part of the effective symbol. Receiving means for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal whose transmission unit is a transmission symbol including the guard interval, and one of the OFDM signals received by the receiving means Timing synchronization means for generating a start flag indicating a timing for cutting out a calculation range for an effective symbol period from a transmission symbol, and generating a phase correction amount indicating a deviation from a reference calculation range for the calculation range cut out by the start flag And according to the start flag generated by the timing synchronization means, Processing to extract the calculation range for the effective symbol period from the OFDM signal received by the receiving means, and rearrange the data order based on the phase correction amount for the extracted OFDM signal in the calculation range And a Fourier transform means for performing a Fourier transform thereafter.

  The Fourier transform means, as a process of rearranging the data order or a process equivalent to the process, when the shift is forward with respect to the start position of the reference calculation range, the calculation cut out according to the start flag A process of shifting the start position of the Fourier transform by the amount corresponding to the phase correction amount backward from the start position of the range or a process equivalent to the process is executed, and the shift is backward with respect to the start position of the reference calculation range. In some cases, a process of shifting the start position of the Fourier transform by an amount corresponding to the phase correction amount from the start position of the calculation range cut out according to the start flag or a process equivalent to the process is executed.

  The timing synchronization means further uses a predetermined one of the plurality of transmission symbols constituting the OFDM signal received by the reception means as a reference symbol, and an arbitrary symbol for the effective symbol period of the reference symbols. A range is set as the reference calculation range.

  The Fourier transform means includes a memory capable of storing OFDM signals for at least effective symbols, stores the OFDM signals in the calculation range cut out according to the start flag in the memory, and rearranges the data order or As a process equivalent to the process, a read address of the memory is generated based on the phase correction amount, and the OFDM signal is read from the memory according to the address and subjected to Fourier transform.

  The Fourier transform means adds an offset corresponding to the phase correction amount to the address value of the start position of the calculation range for the OFDM signal of the calculation range stored in the memory, and the value range in the effective symbol period Is generated as the read address.

  An information processing method and program according to one aspect of the present invention are a method and program corresponding to the information processing apparatus according to one aspect of the present invention described above. The display device according to one aspect of the present invention further includes display means for displaying an image corresponding to the OFDM signal subjected to Fourier transform by the Fourier transform means, with respect to the information processing apparatus according to one aspect of the present invention described above. Prepare.

  In the information processing device and method, the display device, and the program according to one aspect of the present invention, an effective symbol generated by dividing information into frequency components within a predetermined band, and a part of the effective symbol An Orthogonal Frequency Division Multiplexing (OFDM) signal whose transmission unit is a transmission symbol including a guard interval generated by copying a signal waveform is received and 1 in the received OFDM signal. A start flag indicating the timing for cutting out the calculation range for the effective symbol period is generated from the two transmission symbols, and a phase correction amount indicating a deviation from the reference calculation range for the calculation range cut out by the start flag is generated, According to the generated start flag, a valid signal is received from the received OFDM signal. The calculation range for the Vol period is cut out, and the OFDM signal in the cut out calculation range is subjected to processing for rearranging the data order based on the phase correction amount or processing equivalent to the processing, and thereafter Fourier transform is performed. Further, in the display device according to one aspect of the present invention, an image corresponding to the OFDM signal subjected to Fourier transform is displayed.

  As described above, according to the present invention, in particular, the circuit scale of the OFDM receiver can be reduced.

[Conventional explanation]
First, in order to facilitate the understanding of the present invention, the cause of the contents described in [Problems to be Solved by the Invention] will be described with reference to FIGS.

  FIG. 1 shows a configuration example of a transmission signal by the OFDM method.

  As shown in FIG. 1, a transmission signal according to the OFDM scheme is transmitted in units of symbols called OFDM symbols. The OFDM symbol includes an effective symbol that is a signal period during which IFFT is performed at the time of transmission, and a guard interval in which a partial waveform of the latter half of the effective symbol is copied as it is.

  FIG. 2 shows an example of a DFT calculation range for a transmission signal by the OFDM method.

As shown in FIG. 2, hereinafter, N _g is adopted as a symbol representing the OFDM guard interval length, and Nu is adopted as a symbol representing the OFDM effective symbol length. In addition, L is adopted as a symbol representing the deviation of the start position of the DFT operation with respect to the OFDM signal.

The DFT calculation result when L = 0, that is, the DFT calculation result when the DFT calculation range (effective symbol length) matches the effective symbol is expressed as X [k] (k = 0, 1,..., N _u ). In this case, X [k] is expressed by the following equation (1). It is assumed that the relationship of Expression (2) is established.

・・・（１）

... (1)

・・・（２）

... (2)

In addition, the DFT operation result when L = 1 is described as X ′ [k] (k = 0, 1,..., N _u ). In this case, X ′ [k] is expressed by the following equation (3). It is assumed that the relationship of Expression (2) is established.

・・・（３）

... (3)

  From the equations (1) and (3), the DFT calculation result X ′ [k] when L = 1 is expressed by the following equation (4).

・・・（４）

... (4)

The following can be understood from the result of the equation (4). That is, when the start position of the DFT calculation is shifted by 1, the phase is rotated by W _Nu ^kl . Further, when the shift of the start position of the DFT calculation changes from l to l ′, the phase rotates by W _Nu ^{k (l−l ′)} .

  For this reason, conventionally, as shown in FIG. 3, a rotator is provided after the DFT in order to correct this phase shift.

  FIG. 3 shows an example of a configuration around a portion that performs DFT calculation in a conventional OFDM receiver.

  As shown in FIG. 3, the conventional OFDM receiver includes a DFT (FFT) calculation unit 11, a timing synchronization unit 12, and a phase correction unit (rotation unit) 13.

  That is, as a method for correcting the phase (hereinafter referred to as a phase correction method), a method that requires a rotator such as the phase correction unit 13 has been conventionally employed.

[Method of the present invention]

  Therefore, the present inventors have invented a phase correction method (hereinafter referred to as the phase correction method of the present invention) without requiring a rotator such as the phase correction unit 13.

  FIG. 4 is a diagram for explaining the outline of the phase correction method of the present invention.

  4, A in FIG. 4 below the OFDM symbol shows the first DFT calculation range as a reference, and B in FIG. 4 shows the second DFT calculation range when phase correction is not performed. It is shown.

  In the second DFT calculation range in B of FIG. 4, a shift 1 occurs with respect to the first DFT calculation range in A of FIG. 4.

  Therefore, in the phase correction method of the present invention, as shown in FIG. 4C, the data Dl of the portion of the deviation l among the OFDM symbols belonging to the second DFT calculation range is the last of the second DFT calculation range. After being moved to the tail, the DFT operation is performed. That is, the data range shown in D of FIG. 4 is the second DFT calculation range in which phase correction is performed. In the example of FIG. 4, the shift l is an example that is forward with respect to the start position of the first DFT calculation range. However, the deviation l may be backward with respect to the start position of the first DFT calculation range. The handling in such a case will be described later with reference to FIG.

[Configuration example of OFDM receiving apparatus to which the present invention is applied]

  FIG. 5 shows a configuration example of an OFDM receiving apparatus as an embodiment of an information processing apparatus to which the present invention is applied.

  An OFDM receiver 100 includes an antenna 101, a tuner 102, a band pass filter (BPF) 103, an A / D converter 104, an orthogonal demodulator 105, a DFT (FFT) calculator 106, a transmission path distortion corrector 107, and an error corrector. 108 and a display unit 109.

[Operation example of OFDM receiver to which the present invention is applied]

  Hereinafter, an operation example of the OFDM receiving apparatus 100 will be described.

  A broadcast wave broadcast from a broadcast station is received by the antenna 101 of the OFDM receiver 100 and supplied to the tuner 102 as an RF signal.

  The tuner 102 includes a multiplication unit 102a and a local oscillation unit 102b. The tuner 102 converts the RF signal received from the antenna 101 into an IF signal.

  The IF signal obtained by the tuner 102 is filtered by the bandpass filter 103, digitized by the A / D conversion unit 104, and supplied to the orthogonal demodulation unit 105.

  The orthogonal demodulation unit 105 performs orthogonal demodulation on the digitized IF signal using a carrier signal having a predetermined frequency (carrier frequency), and outputs a baseband OFDM signal.

  The baseband OFDM signal output from the orthogonal demodulation unit 105 is a so-called OFDM time domain signal before DFT calculation. As a result of orthogonal demodulation, the OFDM time domain signal becomes a complex signal including a real axis component (I channel signal) and an imaginary axis (Q channel signal).

  The DFT operation unit 106 extracts a signal interval for performing DFT from the OFDM time domain signal using the start flag and the phase correction amount supplied from the timing synchronization unit 110, and performs DFT operation. As a result, data transmitted for each subcarrier is extracted and output from the DFT operation unit 106. The signal output from the DFT calculation unit 106 is a so-called frequency domain signal after DFT. Therefore, hereinafter, the signal after the DFT calculation is referred to as an OFDM frequency domain signal. The OFDM frequency domain signal is provided to the transmission path distortion correction unit 107.

  The transmission path distortion correction unit 107 corrects the distortion of the amplitude and phase received by the OFDM frequency domain signal on the transmission path based on the estimated transmission path characteristics, and supplies the corrected signal to the error correction unit 108 as an equalized signal.

  Error correction section 108 performs deinterleaving processing on the signal interleaved on the transmission side. The decoded data is output from the error correction unit 108 through depuncture, Viterbi decoding, spread signal removal, and RS decoding.

  The display unit 109 displays a video corresponding to the decoded data output from the error correction unit 108.

  6 and 7 are diagrams illustrating detailed examples of operations of the timing synchronization unit 110 and the DFT operation unit 106. FIG.

  In FIG. 6, A of FIG. 6 below the OFDM symbol shows the DFT calculation range of the reference symbol. That is, the timing synchronization unit 110 determines a predetermined OFDM symbol as a reference symbol and sets the DFT calculation range as the reference range. When another OFDM symbol is a target of DFT computation (hereinafter, the OFDM symbol subject to DFT computation is referred to as a target symbol), timing synchronization section 110 shifts the DFT computation range of the target symbol from the reference range. Is detected as a phase correction amount. The timing synchronization unit 110 supplies the phase correction amount of the target symbol to the DFT calculation unit 106.

  The timing synchronization unit 110 generates a start flag indicating the start position of the DFT calculation range of the target symbol and supplies the start flag to the DFT calculation unit 106.

  Specifically, for example, when the symbol α in B of FIG. 6 is the target symbol, the phase correction amount lα and the start symbol SFα are supplied to the DFT calculation unit 106. In this case, as shown in A of FIG. 7, the DFT operation unit 106 outputs the data for the phase correction amount lα arranged behind the start position (the position of the start flag SFα) of the DFT operation range of the target symbol. It is determined as data Dlα to be moved. The DFT calculation unit 106 performs the DFT calculation after moving the data Dlα to the rear of the DFT calculation range of the target symbol. In other words, the DFT calculation unit 106 performs the DFT calculation by shifting the DFT start position backward by the phase correction amount lα from the start position (start flag SFα position) of the DFT calculation range of the target symbol.

  Further, for example, when the symbol β of C in FIG. 6 is the target symbol, the phase correction amount lβ and the start symbol SFβ are supplied to the DFT operation unit 106. In this case, as shown in FIG. 7B, the DFT operation unit 106 determines the data corresponding to the phase correction amount lβ arranged forward from the tail of the DFT operation range of the target symbol as the data Dlβ to be moved. To do. The DFT calculation unit 106 moves the data Dlβ to the front of the DFT calculation range (the position of the start flag SFβ) of the target symbol, and then performs DFT calculation according to the start symbol SFβ. In other words, the DFT calculation unit 106 performs DFT calculation by shifting the DFT start position forward by the phase correction amount lα from the start position (start flag SFα position) of the DFT calculation range of the target symbol.

  FIG. 8 is a flowchart showing an example of the operation of the above OFDM receiver as OFDM demodulation processing.

  In step S <b> 1, the tuner 102 converts the RF signal received by the receiving antenna 101 into an IF signal, and outputs the IF signal to the A / D converter 104 via the BPF 103.

  In step S <b> 2, the A / D conversion unit 104 performs A / D conversion on the IF signal and outputs the digital IF signal to the orthogonal demodulation unit 105.

  In step S <b> 3, the quadrature demodulation unit 105 performs quadrature demodulation on the digitized IF signal and outputs the resulting OFDM time domain signal to the DFT calculation unit 106 and the timing synchronization unit 110.

  In step S <b> 4, the DFT calculation unit 106 performs DFT calculation processing using the start flag and the phase correction amount from the timing synchronization unit 110. The OFDM frequency domain signal obtained by performing the DFT calculation process is output to the transmission path distortion correction unit 107. Details of the FFT calculation processing will be described later with reference to the flowchart of FIG.

  In step S5, the transmission path distortion correction unit 107 corrects the transmission path distortion with respect to the OFDM frequency domain signal and supplies it to the error correction unit 108 as an equalized signal.

  In step S6, the error correction unit 108 performs deinterleaving processing on the signal interleaved on the transmission side. As a result, decoded data is output from the error correction unit 108, and a video corresponding to the decoded data is displayed on the display unit 109.

  FIG. 9 is a flowchart for explaining a detailed example of the DFT calculation process in step S4 of FIG.

  In step S21, the timing synchronization unit 110 determines whether or not it is the first DFT calculation.

  In the case of the first DFT calculation, it is determined as YES in Step S21, and the process proceeds to Step S22. In step S22, the timing synchronization unit 110 sets the target symbol as a reference symbol. In step S23, the timing synchronization unit 110 sets the phase correction amount to zero.

  On the other hand, if it is the second or subsequent DFT calculation, it is determined as NO in step S21, and the process proceeds to step S24. In step S24, the timing synchronization unit 110 detects the phase correction amount of the target symbol.

  In step S25, the timing synchronization unit 110 generates a start flag indicating the start position of the DFT calculation of the target symbol.

  In step S <b> 26, the timing synchronization unit 110 outputs the start flag and the phase correction amount to the DFT calculation unit 106.

  In step S27, the DFT calculation unit 106 determines whether or not the shift is in the forward direction with respect to the start position of the DFT calculation range of the reference symbol.

  For example, if the symbol α of B in FIG. 6 described above is the target symbol, it is determined as YES in Step S27, and the process proceeds to Step S28. In step S28, the DFT calculation unit 106 shifts the start position of the DFT calculation by the amount of phase correction backward from the start position (start flag position) of the DFT calculation range of the target symbol. For example, when the symbol α of B in FIG. 6 described above is the target symbol, as shown in A of FIG. 7, the phase correction amount lα is moved backward from the start position (position of the start flag SFα) of the DFT calculation range of the target symbol. The start position of the DFT calculation is shifted by that amount.

  On the other hand, for example, when the symbol β in FIG. 6 described above is the target symbol, it is determined as NO in step S27, and the process proceeds to step S29. In step S29, the DFT calculation unit 106 shifts the start position of the DFT calculation by the amount of phase correction forward from the start position (start flag position) of the DFT calculation range of the target symbol. For example, in the case where the symbol β in FIG. 6 described above is the target symbol, as shown in FIG. 7B, the phase correction amount lβ is moved forward from the start position (start flag SFβ position) of the DFT calculation range of the target symbol. The start position of the DFT calculation is shifted by that amount.

  In step S30, the DFT calculation unit 106 performs DFT calculation within the DFT calculation range of the target symbol from the start position of the DFT calculation shifted in the process of step S28 or S29.

  Note that the DFT calculation processing is not particularly limited to the example of FIG. For example, it is assumed that the DFT calculation unit 106 can temporarily store an input (data to be DFT) in a memory. It should be noted that once the input is stored in the memory, it is a conventional practice. That is, it should be noted that the circuit scale does not increase by storing the input in the memory once.

  Specifically, for example, as shown in FIG. 10, it is assumed that a memory capable of storing at least the effective symbol length is provided in the DFT operation unit 106. In this case, the original DFT calculation range data of the target symbol is temporarily stored in the memory. Therefore, the DFT calculation unit 106 generates a memory read address based on the phase correction amount, and can read out an OFDM signal from the memory according to the address and perform DFT conversion.

  That is, the DFT calculation unit 106 can realize a process equivalent to the process of step S28 or S29 described above by performing the DFT calculation while shifting the memory reading position by the phase correction amount.

  Specifically, for example, the DFT calculation unit 106 performs DFT calculation by giving an offset corresponding to the phase correction amount to the read position of the memory. That is, the DFT calculation unit 106 adds an offset corresponding to the phase correction amount to the address value at the head position of the original DFT calculation range for the OFDM signal in the original DFT calculation range stored in the memory, Generate an offset address with the range of values adjusted in the period. The DFT calculation unit 106 reads the OFDM signal from the memory according to the offset address and performs DFT calculation. As a result, it is possible to realize a process equivalent to performing the DFT calculation by shifting the start position of the DFT calculation from the start position of the target symbol (the position of the start flag SF) by the phase correction amount l.

  By the way, the series of processes described above can be executed by hardware, but can also be executed by software.

  In this case, for example, a personal computer shown in FIG. 11 may be employed as at least a part of the information processing apparatus to which the present invention is applied.

  In FIG. 11, a CPU (Central Processing Unit) 201 executes various processes according to a program recorded in a ROM (Read Only Memory) 202 or a program loaded from a storage unit 208 to a RAM (Random Access Memory) 203. To do. The RAM 203 also appropriately stores data necessary for the CPU 201 to execute various processes.

  The CPU 201, the ROM 202, and the RAM 203 are connected to each other via the bus 204. An input / output interface 205 is also connected to the bus 204.

  The input / output interface 205 includes an input unit 206 such as a keyboard and a mouse, an output unit 207 including a display, a storage unit 208 including a hard disk, and a communication unit 209 including a modem and a terminal adapter. It is connected. The communication unit 209 controls communication performed with other devices (not shown) via a network including the Internet.

  A drive 210 is also connected to the input / output interface 205 as necessary, and a removable medium 211 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is appropriately installed, and a computer program read from them is loaded. Installed in the storage unit 208 as necessary.

  When a series of processing is executed by software, a program constituting the software executes various functions by installing a computer incorporated in dedicated hardware or various programs. For example, a general-purpose personal computer is installed from a network or a recording medium.

  As shown in FIG. 11, the recording medium including such a program is distributed to provide a program to the user separately from the apparatus main body, and a magnetic disk (including a floppy disk) on which the program is recorded. , Removable media (package media) consisting of optical disks (including CD-ROM (compact disk-read only memory), DVD (digital versatile disk)), magneto-optical disks (including MD (mini-disk)), or semiconductor memory ) 211, but also includes a ROM 202 in which a program is recorded and a hard disk included in the storage unit 208 provided to the user in a state of being incorporated in the apparatus main body in advance.

  In the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in chronological order according to the order, but is not necessarily performed in chronological order, either in parallel or individually. The process to be executed is also included.

  Further, the present invention can be applied to a display device as can be applied to the OFDM receiver 100 including the display unit 109 of FIG. Such a display device can be applied to a display that displays video signals input to various electronic devices or generated in various electronic devices as images or videos. Here, as various electronic devices, for example, there are a digital still camera, a digital video camera, a notebook personal computer, a mobile phone, a television receiver, and the like. Examples of electronic devices to which such a display device is applied are shown below.

  For example, the present invention can be applied to a television receiver which is an example of an electronic device. This television receiver includes a video display screen including a front panel, a filter glass, and the like, and is manufactured by using the display device of the present invention for the video display screen.

  For example, the present invention can be applied to a notebook personal computer which is an example of an electronic device. In this notebook personal computer, the main body includes a keyboard that is operated when characters and the like are input, and the main body cover includes a display unit that displays an image. This notebook personal computer is manufactured by using the display device of the present invention for the display portion.

  For example, the present invention can be applied to a mobile terminal device that is an example of an electronic device. This portable terminal device has an upper housing and a lower housing. As states of the portable terminal device, there are a state in which the two casings are opened and a state in which the two casings are closed. This portable terminal device includes a connecting portion (here, a hinge portion), a display, a sub-display, a picture light, a camera, and the like in addition to the above-described upper housing and lower housing. It is manufactured by using it for sub-displays.

  For example, the present invention is applicable to a digital video camera that is an example of an electronic device. The digital video camera includes a main body, a lens for photographing a subject on a side facing forward, a start / stop switch at the time of photographing, a monitor, and the like, and is manufactured by using the display device of the present invention for the monitor.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a figure explaining the transmission symbol of an OFDM signal. It is a figure which shows an example of the DFT calculation range with respect to the transmission signal by an OFDM system. It is a block diagram which shows the example of a part of structure of the conventional OFDM receiver. It is a figure explaining the outline of the phase correction method of this invention. It is a block diagram which shows the structural example of the OFDM receiver as embodiment of the information processing apparatus with which this invention is applied. FIG. 6 is a diagram illustrating a detailed example of operations of a timing synchronization unit and a DFT calculation unit of the OFDM receiver of FIG. 5. FIG. 6 is a diagram illustrating a detailed example of operations of a timing synchronization unit and a DFT calculation unit of the OFDM receiver of FIG. 5. 6 is a flowchart for explaining an example of OFDM demodulation processing executed by the OFDM receiver of FIG. 5. FIG. 9 is a flowchart for explaining a detailed example of a DFT calculation process of the OFDM demodulation process of FIG. 8. FIG. It is a figure explaining the outline of another example of the phase correction method of this invention. It is a block diagram which shows the structural example of the computer which runs the program with which this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 Antenna, 102 Tuner, 103 Band pass filter, 104 A / D conversion part, 105 Orthogonal demodulation part, 106 DFT calculation part, 107 Transmission path distortion correction part, 108 Error correction part, 109 Display part, 110 Timing synchronization part 201 CPU , 202 ROM, 203 RAM, 208 storage unit, 211 removable media

Claims (8)

A transmission symbol including an effective symbol generated by dividing information into frequency components within a predetermined band and a guard interval generated by copying a signal waveform of a part of the effective symbol Receiving means for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal having a transmission unit as a transmission unit;
A start flag indicating a timing for cutting out a calculation range for an effective symbol period is generated from one transmission symbol in the OFDM signal received by the receiving means, and a reference calculation range for the calculation range cut out by the start flag Timing synchronization means for generating a phase correction amount indicating a deviation from
In accordance with the start flag generated by the timing synchronization unit, the calculation range for the effective symbol period is cut out from the OFDM signal received by the reception unit, and the phase of the calculated OFDM signal in the calculation range is extracted. An information processing apparatus comprising: a Fourier transform unit that performs a process of rearranging the data order based on the correction amount or a process equivalent to the process, and then performs a Fourier transform. The Fourier transform means includes
As a process of rearranging the data order or a process equivalent to the process,
When the shift is forward with respect to the start position of the reference calculation range, the Fourier transform start position is shifted backward by the phase correction amount from the start position of the calculation range cut out according to the start flag. Execute the process or equivalent process,
When the shift is backward with respect to the start position of the reference calculation range, the Fourier transform start position is shifted forward by the phase correction amount from the start position of the calculation range cut out according to the start flag. The information processing apparatus according to claim 1, wherein a process or a process equivalent to the process is executed. The timing synchronization means further includes
A predetermined one of the plurality of transmission symbols constituting the OFDM signal received by the receiving unit is used as a reference symbol, and an arbitrary range for the effective symbol period of the reference symbols is used as the reference calculation range. The information processing apparatus according to claim 1 to be set. The Fourier transform means includes
Having a memory capable of storing at least OFDM signals for effective symbols;
Store the OFDM signal of the calculation range cut out according to the start flag in the memory,
As a process for rearranging the data order or a process equivalent to the process, a read address of the memory is generated based on the phase correction amount,
The information processing apparatus according to claim 1, wherein the OFDM signal is read from the memory according to the address and subjected to Fourier transform. The Fourier transform means includes
For an OFDM signal in the calculation range stored in the memory, an offset address obtained by adjusting the value range in an effective symbol period by adding an offset corresponding to the phase correction amount to the address value at the start position of the calculation range The information processing apparatus according to claim 4, wherein the information is generated as the read address. A transmission symbol including an effective symbol generated by dividing information into frequency components within a predetermined band and a guard interval generated by copying a signal waveform of a part of the effective symbol An information processing apparatus that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal having a transmission unit as a transmission unit,
A start flag indicating a timing for cutting out a calculation range for an effective symbol period is generated from one transmission symbol in the received OFDM signal, and a deviation from a reference calculation range for the calculation range cut out by the start flag is determined. Generate a phase correction amount
According to the generated start flag, the calculation range for the effective symbol period is cut out from the received OFDM signal, and the data order is arranged based on the phase correction amount for the cut out OFDM signal in the calculation range. An information processing method including a step of performing a replacement process or a process equivalent to the process and then performing a Fourier transform. A transmission symbol including an effective symbol generated by dividing information into frequency components within a predetermined band and a guard interval generated by copying a signal waveform of a part of the effective symbol In a computer that controls a receiving device that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal having a transmission unit as a transmission unit,
A start flag indicating a timing for cutting out a calculation range for an effective symbol period is generated from one transmission symbol in the received OFDM signal, and a deviation from a reference calculation range for the calculation range cut out by the start flag is determined. Generate a phase correction amount
According to the generated start flag, the calculation range for the effective symbol period is cut out from the received OFDM signal, and the data order is arranged based on the phase correction amount for the cut out OFDM signal in the calculation range. A program that executes a control process including a step of performing a process to be replaced or a process equivalent to the process and then performing a Fourier transform. A transmission symbol including an effective symbol generated by dividing information into frequency components within a predetermined band and a guard interval generated by copying a signal waveform of a part of the effective symbol Receiving means for receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal having a transmission unit as a transmission unit;
A start flag indicating a timing for cutting out a calculation range for an effective symbol period is generated from one transmission symbol in the OFDM signal received by the receiving means, and a reference calculation range for the calculation range cut out by the start flag Timing synchronization means for generating a phase correction amount indicating a deviation from
In accordance with the start flag generated by the timing synchronization unit, the calculation range for the effective symbol period is cut out from the OFDM signal received by the reception unit, and the phase of the calculated OFDM signal in the calculation range is extracted. Fourier transform means for performing a process for rearranging the data order based on the correction amount or a process equivalent to the process, and then performing a Fourier transform;
A display device comprising: display means for displaying an image corresponding to the OFDM signal subjected to Fourier transform by the Fourier transform means.

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